Why your sms cannot deliver?

Well that's a very tricky question of coarse it matters on your phone company I love Verizon Wireless over AT&T but an sms not sending has happened to me before sometimes the cause is that there has been to much txtng going on and that the screen freezes up but I would suggest that you turn your phone off and let sit there for about 30 seconds without turning it on then turn it on retype your message and send it it will definitely work trust me.